Prior wide field ophthalmic lenses are known in the art. One of these is disclosed in Erickson et al., U.S. Pat. No. 5,007,729 assigned to the assignee hereof. The Erickson et al. patent discloses a three element lens that provides a high quality wide field of view of the fundus and of the peripheral retinal region. It is desirable, however, in many instances to have an even wider field of view so that the region adjacent and anterior to the equator of the eye can be viewed without manipulating the lens position relative to the eye. However, a change in the lens position can only slightly improve the range of view in only a portion of the peripheral portion.
Further increasing the field of view beyond that provided, for example, by the lens of the Erickson et al. patent, requires significant design changes to the lenses, particularly to the entry and intermediate lenses. The rays emanating from the peripheral portions of the eye adjacent and anterior to the equator rays must travel through the crystalline lens, pupil and cornea at even increasing angles relative to the optical axis of the lens. In order to refract these light rays and provide a usable image, all of the lenses, and particularly the entry and intermediate lenses, using prior art design techniques, must be given an ever-increasing diameter. As the diameter of the lens increases so does the overall diameter of the compound system as well as its axial length. Increasing the diameter much beyond that disclosed in the Erickson et al. patent, however, will provide a lens that is impractical to use even though it might be capable of providing a wider field.